These two terms have often been confused, but they describe different patterns of vegetation that are mostly, though not always, associated with tropical climates. “Jungle” is a general term used to describe vegetation that is tangled and impenetrable — the kind that might seriously impede the progress of humans, and which may need to be cut through with tools such as machetes. It comes from the Sanskrit word jangala, which simply means uncultivated land. A rainforest is a type of dense forest, often with several layers of vegetation, that is found in areas of high rainfall. The foliage in the upper parts is generally so dense that relatively little light reaches the ground, and because of this, ground-level plant life is quite sparse — it is, in fact, much easier to walk through rainforest than jungle.
Much early exploration of tropical forests by Europeans took place via rivers. Around these rivers, vegetation was usually very dense, as much more light was able to reach the ground in the absence of trees. Consequently, it was assumed that the impenetrable-looking vegetation visible around the rivers was typical of the forest, and the term “jungle” came to be used to describe rainforests.
In the past, the word jungle has been used rather indiscriminately to describe almost any kind of dense, tropical vegetation, including what is now called rainforest. The term “rainforest”, however, only came into common use in the 1970s. Plants need both moisture and light to grow well, and the kind of dense ground-level vegetation that thrives in jungle areas occurs in places that have plentiful rainfall for at least part of the year, and more or less unrestricted access to sunlight. Consequently, it differs markedly from rainforest.
Jungle, however, may well occur close to, and within, rainforests, since all that is usually required in these warm, moist areas for this type of vegetation to develop is an adequate supply of light. Therefore, in places where trees are sparse, jungle can thrive. Typically, jungle vegetation will be found at the edges of rainforests, along rivers within the forest, and in areas where trees have fallen due to natural disasters such as high winds, or where trees have been felled by humans, and the land then left to itself.
This kind of vegetation is not found in temperate areas, as constant high temperatures are required to allow the year-round growth of plants. When combined with moist conditions, and a plentiful supply of light, growth is rapid. Many kinds of plants have evolved to compete successfully for resources, and so jungle areas, like rainforests, have a great diversity of plant life; however, the main difference is in the ground level vegetation. Trees do not get a chance to grow, as faster spreading plants rapidly deprive small seedlings of space and light. Plants in these areas have evolved to grow and spread quickly, and in many cases possess thorns to defend themselves against predators, resulting in a thick, impenetrable tangle of plants that makes life difficult for explorers.
As the name implies, this type of vegetation occurs in areas of high rainfall. In the equatorial regions, conditions are ideal for rainforest, due to the frequent heavy rain, high humidity and year-round high temperatures. Rainforests, can, however, be found in some temperate regions, where rainfall is high enough. For example, many parts of the west coast of North America have forests of this type. These woodlands, however, have far fewer plant and animal species living in them than tropical forests.
The typical tropical rainforest has a high canopy of overlapping branches and leaves that absorb most of the incoming sunlight. The trees that make up this layer generally grow to between 70 and 100 feet (21 - 30 meters). Above this, there may be an emergent layer, consisting of a relatively small number of even taller trees, up to 180 ft (55 m) high. Below the main canopy, there is a shrub, or understory, layer, consisting of young trees and large-leaved plants that are able to exploit the relatively small amounts of light at this level. The ground layer has only a few shade-loving plants.